IMPROVEMENTS IN AND RELATING TO GRINDING MACHINES

Abstract: A grinding machine having a relatively movable worktable (64) and grinding wheel (66) which can be swivelled, the positions of a tailstock (62) and workrests (60, 61) being adjustable by computer controlled drive means relative to the worktable to enable different components (and parts thereof) to be ground on the same machine.

Description: Title: Improvements in and relating to Grinding Machines Field of the invention This invention concerns grinding machines and in particular improvements thereto whereby different workpiece components (or different parts of the same workpiece) can be ground on the same machine. Background to the invention Historically grinding machines have tended to be set up to grind large numbers of one particular component such as a cam shaft for a motor car engine. With the trend towards a greater variety of engines the need to be able to produce smaller runs of different cam shafts and other ground components has arisen. Rather than provide different machines for grinding the different components thereby occupying valuable workshop space and increasing the overhead component of a business, the present invention provides an alternative solution to this problem. Summary of the invention According to one aspect of the present invention, in a grinding machine having a relatively movable grinding wheel and worktable, at least the tailstock or headstock or workrest are movable by programmable drive means relative to the worktable to enable different workpieces or parts thereof to be positioned in front of a grinding wheel for grinding. The worktable on which the tailstock and headstock and workrest (s) are mounted is itself preferably driven by the programmable drive means . Preferably each of the workrest, tailstock, headstock and worktable is independently driven and the control signals for each drive are independently programmable to enable components of differing length and diameter to be accommodated. The signals for controlling the drives may be derived from one or more computers associated with the machine. The computer is preferably programmed with positional and dimensional information relative to a reference determined by the relative position of the grinding wheel and worktable. According to another feature of the present invention a probe is provided typically but not necessarily towards one end or the other of the workpiece station in a grinding machine which is adapted to be movable towards and away from a workpiece, and in a direction parallel to the workpiece, to enable a part of a workpiece to be located by the probe. By employing such a probe, the precise position of a known part of the workpiece can be determined relative to the position of the grinding wheel and. the position of the workpiece and the position of the workrest is adjusted in relation thereto. Typically the said part of the workpiece comprises a radial face thereof which constitutes a form of benchmark from which machining operations on the workpiece can be positioned. The programming of the relative positions of the workpiece and workrest (s) may be related to the known position so that initially a workpiece may be positioned between a headstock and tailstock without the workrest (s) engaging the workpiece and after the probe has travelled inwardly and sensed the position of the workpiece, as by sensing a radial face thereof, the drive (s) to the workrest (s) can be activated under computer control and the workrest (s) positioned parallel to and/or perpendicular to the workpiece in accordance with pre-programmed information relating to the workpiece which has been loaded into the machine. According therefore to a further feature of the invention, the programmable control means is responsive to positional information from a probe in a grinding machine as aforesaid to provide drive control signals for drives for positioning some or all of the headstock and tailstock assemblies, workrest (s) and/or the worktable to position the latter perpendicularly (and possibly also parallel) to the axis of the workpiece, and to provide further drive control signals to control the wheelfeed drive to advance and retract the grinding wheel as required as the workpiece is advanced axially through the grinding station. According to a still further feature of the invention the grinding wheel is mounted within a wheelhead assembly which itself is movable in a direction perpendicular to the workpiece axis and is also rotatable about a vertical axis orthogonal to the axis about which the wheel rotates which (vertical axis) preferably but not necessarily intersects with the axis about which the wheel rotates, and drive means is provided for angularly rotating the workhead about the vertical axis so as to present the grinding wheel at an angle to the workpiece to perform non-axial grinding. Control signals for the rotatable drive means associated with the wheelhead may also be derived from the computer associated with the machine which also generates or controls the drive control signals for the other programmable drives so that if a workpiece is loaded into a machine which requires non-axial grinding as well as ordinary axial grinding, the wheelhead can be angled accordingly under computer control along with the operation of the other drives to accommodate the particular workpiece which has been loaded into the machine. Description of embodiment The invention is further described by way of example with reference to the accompanying drawings, in which: Figure 1 is a general view of a grinding machine incorporating the invention; Figure 2 is a close-up view showing the probe engaging a radial face of the workpiece; Figure 3 is a close-up view showing the grinding wheel and worksteadys; Figure 4 is an interior view of the machine showing the workhead mounted on the machine base; Figure 5 shows the drive means for rotating the wheelhead about a vertical axis; Figure 6 designates part of a computer program; and Figure 7 is a diagrammatic view of the machine marked to relate with the program of Figure 6. In Figure 1 the main machine bed 10 supports a wheelhead not visible, within the slidable enclosure 12 which can be opened to enable workpieces to be inserted and removed and includes an inspection window 14. A computer based control system 16 stands adjacent the machine and can be manually adjusted to control the machine so as to receive and grind different workpieces according to pre-programmed information. There is shown in Figure 2 a probe 18 which can be seen engaging the radial shoulder 20 of a pre-machined section of the workpiece 22. The probe is adapted to be driven into engagement with the machine diameter of the segment 22 and then moved radially until it engages the radial shoulder it is seeking. Positional information is derived therefrom and sent to the computer control centre 16. The workpiece is also visible in Figure 2 and is denoted by reference numeral 24. Workrests are also visible at 26 and 28 and drive means within the workrests adjusts them perpendicularly to the workpiece and if required laterally relative to the workpiece. Signals for controlling the drives for the workrests 26 and 28 are derived from the control centre 16. Figure 3 shows the same part of the machine as viewed from a more distant point showing the beginning of the headstock assembly 30 and the tailstock at 32. Figure 3 also shows the additional workrests at 34 and 36. Each of the latter includes drives similar to those for workrests 26 and 28 and is operable in the same way from the control centre 16. Also in Figure 3 can be seen the grinding wheel 38. In order to provide a further degree of workpiece customisation, the wheelhead assembly of the grinding machine is mounted on a pivotable platform. Figure 4 shows the wheelhead assembly at 40 mounted on a base 42 which itself is pivotable relative to a sub-base 44 carried on the machine bed 46. By moving the base 42 about a pivot axis (not shown in Figure 4) but preferably orthogonal to the axis of rotation of the grinding wheel, so the angle of attack of the wheel to the workpiece can be adjusted. Drive means for effecting this sliding and thereby pivoting or tilting of the wheelhead assembly 40 is shown in Figure 5. This comprises a hydraulic or pneumatic ram 48 acting between the platform 42 and pivotally mounted at 50 to the sub-base 44. Mounted thereon at 52 is a control device for the ram to enable the latter to be advanced and retracted and control signals from the control sensor 16. In more detail, and making reference to Figures 6 and 7, dimensions taken from a component engineering drawing are directly used as input data to the control via a component part programme (Figure 6) . The dimensions required to manufacture a component are.*- 1. The. lateral positions of cam lobes or plain diameters from a defined lateral reference position (ABSZ) . 2. In the case of a cam lobe, the profile shape of each cam lobe specified as "lift" distances above a specified cam minimum radius (base radius) at specified angles for a specified radius of cam follower and the angle of each cam lobe from a defined angular reference position (PROFILE) . 3. In the case of a plain diameter, the diameter. 4. The angle of inclination of the surface of each cam lobe or plain diameter is specified with reference to the centre-line of rotation of the camshaft (ANGLE) . 5. The lateral position of the work support bearing diameters from the above mentioned defined lateral reference position (ABSZ2, ABSZ3) . 6. The lateral position of a measurement reference face that is perpendicular to the axis of rotation, from the above mentioned defined lateral reference position (ABSZ) . 7. The length of the component (ABSZO) . In Figure 7, the above mentioned information, i.e. ABSZ etc., is marked on the diagrammatically shown machine. Several radial work supports 60, 61 (workrests) and an axial work support 62 (tailstock or footstock) are carried upon the worktable 64 and each is independently positioned by the computer, laterally with respect to the worktable. In the illustration of Figure 7, headstock 71 is fixed relative to the worktable, but this is not necessarily the case. The worktable 64 can also be positioned by the computer, laterally with respect to the grinding wheel 66 on the wheelhead 67. It is apparent that, if the worktable is moved, the workrests, footstock and headstock that are mounted upon the worktable also move. The adjusted position of the worktable defines a lateral reference position 68. The control system uses length information relating to the component 69 to automatically position the footstock upon the worktable, so as to provide the necessary end thrust to properly constrain the component. The control system uses the work support diameter lateral position information to automatically position the workrests upon the worktable, so that they laterally align with the component work support diameters . The control system uses the lateral positions of the cam lobes and plain diameters to automatically position the worktable so that the cam lobes and plain diameters are sequentially brought in front of the grinding wheel so that they may be ground. Variation in lateral position of the cam lobes/plain diameters and work support diameters due to component tolerance variation, e.g. variation in centre depth, is eliminated by use of the electronic measurement probe 70. The probe is automatically advanced, under computer control, at the start of each cycle, after the footstock is positioned to support the component . The worktable is positioned so as to place a measurement reference face 72 at its theoretically correct position with respect to the probe. The probe is advanced onto the measurement face and measures the error in lateral position of the measurement reference face. The measured error is then algebraically summed with the programmed lateral positions of the cam lobes/plain diameters and work support diameters taken from the component drawing so correcting any possible error in lateral position. The angle of inclination of each cam lobe or plain diameter is used automatically to swivel the grinding wheel axis of rotation about a vertical axis to the specified angle before each grind so that the specified surface incline is achieved on the finished component. The cam profile data is used to grind non-round shapes at the specified angular positions.

Claims: Claims 1. A grinding machine having a worktable carrying a headstock, tailstock and workrest, wherein the worktable is movable relatively to the grinding wheel, and at least one of the headstock, tailstock and workrest is movable relative to the worktable, the relative movements being controlled by programmable drive means to enable different workpieces (or different parts of a workpiece) to be positioned in front of the grinding wheel for grinding. 2. A grinding machine according to claim 1, in which each of the headstock, tailstock and workrest are independently drivable by the drive means relative to the worktable. 3. A grinding machine according to claim 1 or claim 2, in which control signals for the drive means are derived from a computer associated with the machine. 4. A grinding machine according to claim 3, in which the computer is programmed with positional and dimensional information relating to the workpiece or parts thereof to be ground. 5. A grinding machine according to claim 4, in which the computer is at least in part programmed with respect to a lateral reference determined by the relative position of the grinding wheel and the worktable, for positioning of the headstock and/or tailstock and/or workrest . 6. A grinding machine according to claim 4 or claim 5, in which the computer is at least in part programmed with respect to a reference provided by a probe adapted to be relatively movable towards and away from the workpiece and in a direction parallel to the axis of the workpiece in order to enable a part of the workpiece to be located by said probe. 7. A grinding machine according to claim 5 or claim 6, in which the computer utilises the relative lateral positions of radial faces of the workpiece automatically to position the worktable so that parts to be ground are sequentially located for grinding by the grinding wheel . 8. A grinding machine according to any of claims 5 to 7, in which the computer utilises information relating to the length of a component automatically to position the tailstock relative to the worktable. 9. A grinding machine according to any of claims 5 to 8, in which the computer utilises component diameter information automatically to position one or more workrests relative to the worktable. 10. A grinding machine according to any of claims 5 to 9, in which the axis of the grinding wheel can be swivelled under control of the computer for the inclined grinding of the workpiece.

Inventors: LAYCOCK MICHAEL, LAYCOCK, MICHAEL
Applicants: LAYCOCK MICHAEL, WESTERN ATLAS UK LTD, LAYCOCK, MICHAEL, WESTERN ATLAS U.K. LIMITED
Application year: 1994
Main classification: B24B19
IPC codes: B24B19, B24B41